I assume it's possible, but it seems like a huge task and I'm not sure where to start. It seems like official support ended with the loss of upstream security patches, which makes sense. I plan on using my phone strictly on trusted wifi and with non-sensitive data, so I'm not overly concerned about device security, I mostly just want it as a test device for developing applications. A side benefit of porting the OS to the device will be getting more familiar with the OS and device interfaces, which I have been meaning to do anyway as I'll need it for some of the apps I have in mind.

I guess my questions are, where should I start? Are there particular pitfalls I should look out for? Will the lack of modern kernel security have implications for the security of apps developed for that platform? Is such a thing even doable / feasible? Should I just use PostmarketOS instead?